Despite the increased public awareness and professional concern over the use of mercury in dental amalgam, only a few research groups have devoted considerable effort to determining the ultimate exposure and biological effects of this element. Therefore, many significant and imperative questions remain unanswered. The importance of this issue lies in the fact that approximately 80% of all posterior restorations are made from this material. The goal of the original research proposal was to systematically investigate the quantity, rate and mechanisms of mercury release from dental amalgams and their constituent phases by dissolution and evaporation. The overall goal of the present proposal is to continue this effort in order to establish maximum values for the level of exposure for dental patients and personnel to mercury from dental amalgams. In addition, further information on the rat, mechanism and chemical form of mercury released from amalgam will be obtained. A gold film mercury analyzer (Jerome 411) will be used to quantitate the vaporization of mercury from liquid mercury, amalgams and amalgam phases through aqueous solutions, as is expected to occur in vivo. The effects of corrosion and fatigue loading on mercury vapor release from amalgam will also be studied. In addition, the total amount of mercury vapor generated during trituration, placement, polishing and removal of amalgam will be quantitated in a closed system with the vapor analyzer, in order to determine the ultimate exposure to both patient and dental personnel. Atomic absorption spectroscopy will be used to quantitate the solubility limits and dissolution rate of mercury in water, saline and an artificial saliva. In addition, this technique will be employed to determine the total amount of mercury, as well as silver, copper, tin and zinc, dissolving from amalgam immersed in a flowing, continuously replenished solution, as would be encountered in vivo. Finally, the rate of formation and composition of the surface film forming on amalgam and its phases in air and saline will be determined by x-ray photoelectron spectroscopy, since this film has been shown to retard mercury emission. It is believed that the present study will more completely evaluate the mechanisms of release, as well as quantitate the total amount of mercury that the dental patient and personnel may be exposed to on a routine basis.